Scott and his Prompt 80

Restoring A Vintage Intel Prompt 80 8080 Microcomputer Trainer

September 3, 2025 by No comments

Over on his blog our hacker [Scott Baker] restores a Prompt 80, which was a development system for the 8-bit Intel 8080 CPU.

[Scott] acquired this broken trainer on eBay and then set about restoring it. The trainer provides I/O for programming, probing, and debugging an attached CPU. The first problem discovered when opening the case is that the CPU board is missing. The original board was an 80/10 but [Scott] ended up installing a newer 80/10A board he scored for fifty bucks. Later he upgraded to an 80/10B which increased the RAM and added a multimodule slot.

[Scott] has some luck fixing the failed power supply by recapping some of the smaller electrolytic capacitors which were showing high ESR. Once he had the board installed and the power supply functional he was able to input his first assembly program: a Cylon LED program! Making artistic use of the LEDs attached to the parallel port. You can see the results in the video embedded below.

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CP/M Gently

September 3, 2025 by 1 Comment

If you are interested in retrocomputers, you might be like us and old enough to remember the old systems and still have some of the books. But what if you aren’t? No one is born knowing how to copy a file with PIP, for example, so [Kraileth] has the answer: A Gentle Introduction to CP/M.

Of course, by modern standards, CP/M isn’t very hard. You had disks and they had a single level of files in them. No subdirectories. We did eventually get user areas, and the post covers that near the end. It was a common mod to treat user 0 as a global user, but by default, no.

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Over-Engineering An Egg Cracking Machine

September 3, 2025 by 7 Comments

Eggs are perhaps the most beloved staple of breakfast. However, they come with a flaw, they are incredibly messy to work with. Cracking in particular leaves egg on one’s hands and countertop, requiring frequent hand washing. This fundamental flaw of eggs inspired [Stuff Made Here] to fix it with an over-engineered egg cracking robot. 

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One Camera Mule To Rule Them All

September 3, 2025 by No comments

A mule isn’t just a four-legged hybrid created of a union betwixt Donkey and Horse; in our circles, it’s much more likely to mean a testbed device you hang various bits of hardware off in order to evaluate. [Jenny List]’s 7″ touchscreen camera enclosure is just such a mule.

In this case, the hardware to be evaluated is camera modules– she’s starting out with the official RPi HQ camera, but the modular nature of the construction means it’s easy to swap modules for evaluation. The camera modules live on 3D printed front plates held to the similarly-printed body with self-tapping screws.

Any Pi will do, though depending on the camera module you may need one of the newer versions. [Jenny] has got Pi4 inside, which ought to handle anything. For control and preview, [Jenny] is using an old first-gen 7″ touchscreen from the Raspberry Pi foundation. Those were nice little screens back in the day, and they still serve well now.

There’s no provision for a battery because [Jenny] doesn’t need one– this isn’t a working camera, after all, it’s just a test mule for the sensors. Having it tethered to a wall wart or power bank is no problem in this application. All files are on GitHub under a CC4.0 license– not just STLs, either, proper CAD files that you can actually make your own. (SCAD files in this case, but who doesn’t love OpenSCAD?) That means if you love the look of this thing and want to squeeze in a battery or add a tripod mount, you can! It’s no shock that our own [Jenny List] would follow best-practice for open source hardware, but it’s so few people do that it’s worth calling out when we see it.

Thanks to [Jenny] for the tip, and don’t forget that the tip line is open to everyone, and everyone is equally welcome to toot their own horn.

Ask Hackaday: Now You Install Your Friends’ VPNs. But Which One?

September 3, 2025 by 34 Comments

Something which may well unite Hackaday readers is the experience of being “The computer person” among your family or friends. You’ll know how it goes, when you go home for Christmas, stay with the in-laws, or go to see some friend from way back, you end up fixing their printer connection or something. You know that they would bridle somewhat if you asked them to do whatever it is they do for a living as a free service for you, but hey, that’s the penalty for working in technology.

Bad Laws Just Make People Avoid Them

There’s a new one that’s happened to me and no doubt other technically-minded Brits over the last few weeks: I’m being asked to recommend, and sometimes install, a VPN service. The British government recently introduced the Online Safety Act, which is imposing ID-backed age verification for British internet users when they access a large range of popular websites. The intent is to regulate access to pornography, but the net has been spread so wide that many essential or confidential services are being caught up in it. To be a British Internet user is to have your government peering over your shoulder, and while nobody’s on the side of online abusers, understandably a lot of my compatriots want no part of it. We’re in the odd position of having 4Chan and the right-wing Reform Party alongside Wikipedia among those at the front line on the matter. What a time to be alive.

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A hand holding a One ROM with a Commodore 64 in the background

One ROM: The Latest Incarnation Of The Software Defined ROM

September 3, 2025 by 8 Comments

Retrocomputers need ROMs, but they’re just so read only. Enter the latest incarnation of [Piers]’s One ROM to rule them all, now built with a RP2350, because the newest version is 5V capable. This can replace the failing ROMs in your old Commodore gear with this sweet design on a two-layer PCB, using a cheap microcontroller.

[Piers] wanted to use the RP2350 from the beginning but there simply wasn’t space on the board for the 23 level shifters which would have been required. But now that the A4 stepping adds 5 V tolerance [Piers] has been able to reformulate his design.

The C64 in the demo has three different ROMs: the basic ROM, kernel ROM, and character ROM. A single One ROM can emulate all three. The firmware is performance critical, it needs to convert requests on the address pins to results on the data bus just as fast as it can and [Piers] employs a number of tricks to meet these requirements.

The PCB layout for the RP2350 required extensive changes from the larger STM32 in the previous version. Because the RP2350 uses large power and ground pads underneath the IC this area, which was originally used to drop vias to the other side of the board, was no longer available for signal routing. And of course [Piers] is constrained by the size of the board needing to fit in the original form factor used by the C64.

The One ROM code is available over on GitHub, and the accompanying video from [Piers] is an interesting look into the design process and how tradeoffs and compromises and hacks are made in order to meet functional requirements.

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